MadSci Network: Genetics


Area: Genetics
Posted By: Michael Onken, WashU
Date: Mon Nov 4 17:00:58 1996

What did Griffin's experiment (the one in genetics, about DNA) show,
and what is the genetic code of protiens for: UAC, CAG, AUU, CCA?
Thanx so much

Dr. Fred Griffith was a bacteriologist working on the pneumococcus (Streptococcus pneumoniae), the bacterium that cause pneumonia. During his studies, he determined that pneumococci come in two forms: one formed smooth, glossy colonies on agar and could cause pneumonia when injected into mice (he called this strain "S" for smooth); the other formed rough, fluffy colonies and had no affect when injected into mice (he called this strain "R" for rough). So here's the ground-breaking experiment:

In 1928, Griffith injected into mice single and mixed strains of pneumococcus which had or had not been heat-inactivated (killed), and got the following results:

Live Strain(s)                    Killed Strain(s)                    Effect on Mice

     -                                  -                                 Alive
     -                                  R                                 Alive
     -                                  S                                 Alive
     R                                  -                                 Alive
     S                                  -                                 Dead
     R                                  S                                 Dead
     S                                  R                                 Dead

The important point is that mixing the live R bacteria with the killed S bacteria produced pneumonia in the mice; in fact, bacteria cultured from the mice infected this way grew as smooth, glossy colonies, which meant that the R strain had been "transformed" into the S strain by something (Griffith called it the "transforming factor") that had been in the dead S bacteria. In fact, further experiments showed that this factor was inherited by each generation and acted just like a gene. This meant that genes existed as physical things which were preserved even after the organism died, and that this genetic material can be transfered from one organism to another while preserving its function.

Several years later, in 1944, Dr. Oswald Avery isolated this genetic material that was being transfered between the bacteria, and determined that it was a chemical found in cell nuclei called DeoxyriboNucleic Acid, or DNA.

To answer the second part of your question, based on universal codon usage, the mRNA sequence, UAC, CAG, AUU, CCA, would yield the tetrapeptide, Tyr-Gln-Ile-Pro (YQIP).

Current Queue | Current Queue for Genetics | Genetics archives

Try the links in the MadSci Library for more information on Genetics.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci
MadSci Network